Inflammation
Human peripheral blood is composed principally of red blood cells, platelets and white blood cells or leukocytes. The family of leukocytes are further classified as neutrophils, lymphocytes (mostly B- and T-cell subtypes), monocytes, eosinophils and basophils. Neutrophils, eosinophils and basophils are sometimes referred to as “granulocytes” or “polymorphonuclear (PMN) granulocytes” because of the appearance of granules in their cytoplasm and their multiple nuclei. Granulocytes and monocytes are often classified as “phagocytes” because of their ability to phagocytose or ingest micro-organisms and foreign mater referred to generally as “antigens”. Monocytes are so called because of their large single nucleus and these cells may in turn become macrophages. Phagocytes are important in defending the host against a variety of infections and together with lymphocytes are also involved in inflammatory disorders. The neutrophil is the most common leukocyte found in human peripheral blood followed closely by the lymphocyte. In a microliter of normal human peripheral blood, there are about 6,000 leukocytes, of which about 4,000 are neutrophils, 1500 are lymphocytes, 250 are monocytes, 150 are eosinophils and 25 are basophils.
During an inflammatory response peripheral blood leukocytes are recruited to the site of inflammation or injury by a series of specific cellular interactions (see FIG. 1). The initiation and maintenance of immune functions are regulated by intercellular adhesive interactions as well as signal transduction resulting from interactions between leukocytes and other cells. Leukocyte adhesion to vascular endothelium and migration from the circulation to sites of inflammation is a critical step in the inflammatory response (FIG. 1). T-cell lymphocyte immune recognition requires the interaction of the T-cell receptor with antigen (in combination with the major histocompatibility complex) as well as adhesion receptors, which promote attachment of T-cells to antigen-presenting cells and transduce signals for T-cell activation. The lymphocyte function associated antigen-1 (LFA-1) has been identified as the major integrin that mediates lymphocyte adhesion and activation leading to a normal immune response, as well as several pathological states (Springer, T. A., Nature 346:425-434 (1990)). Intercellular adhesion molecules (ICAM) −1, −2, and −3, members of the immunoglobulin superfamily, are ligands for LFA-1 found on endothelium, leukocytes and other cell types. The binding of LFA-1 to ICAMs mediate a range of lymphocyte functions including lymphokine production of helper T-cells in response to antigen presenting cells, T-lymphocyte mediated target cells lysis, natural killing of tumor cells, and immunoglobulin production through T-cell-B-cell interactions. Thus, many facets of lymphocyte function involve the interaction of the LFA-1 integrin and its ICAM ligands. These LFA-1:ICAM mediated interactions have been directly implicated in numerous inflammatory disease states including; graft rejection, dermatitis, psoriasis, asthma and rheumatoid arthritis.
While LFA-1 (CD11a/CD18) on lymphocytes plays a key role in chronic inflammation and immune responses, other members of the leukocyte integrin family (CD11b/CD18, CD11c/CD18 and CD11d/CD18) also play important roles on other leukocytes, such as granulocytes and monocytes, particularly in early response to infective agents and in acute inflammatory response.
The primary function of polymorphonuclear leukocytes, derived from the neutrophil, eosinophil and basophil lineage, is to sense inflammatory stimuli and to emigrate across the endothelial barrier and carry out scavenger function as a first line of host defense. The integrin Mac-1(CD11b/CD18) is rapidly upregulated on these cells upon activation and binding to its multiple ligands which results in the release of oxygen derived free radicals, protease's and phospholipases. In certain chronic inflammatory states this recruitment is improperly regulated resulting in significant cellular and tissue injury. (Harlan, J. M., Acta Med Scand Suppl., 715:123 (1987); Weiss, S., New England J. of Med., 320:365 (1989)).
LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18)
The (CD11/CD18) family of adhesion receptor molecules comprises four highly related cell surface glycoproteins; LFA-1 (CD11a/CD18), Mac-1 (CD11b/CD18), p150.95 (CD11c/CD18) and (CD11d/CD18). LFA-1 is present on the surface of all mature leukocytes except a subset of macrophages and is considered the major lymphoid integrin. The expression of Mac-1, p150.95 and CD11d/CD18 is predominantly confined to cells of the myeloid lineage (which include neutrophils, monocytes, macrophage and mast cells). Functional studies have suggested that LFA-1 interacts with several ligands, including ICAM-1 (Rothleinet al., J. Immunol. 137:1270-1274 (1986), ICAM-2, (Staunton et al., Nature 339:361-364 (1989)), ICAM-3 (Fawcett et al., Nature 360:481-484 (1992); Vezeux et al., Nature 360:485-488, (1992); de Fougerolles and Springer, J. Exp. Med. 175:185-190 (1990)) and Telencephalin (Tian et al., J. Immunol. 158:928-936 (1997)).
The CD11/CD18 family is related structurally and genetically to the larger integrin family of receptors that modulate cell adhesive interactions, which include; embryogenesis, adhesion to extracellular substrates, and cell differentiation (Hynes, R. O., Cell 48:549-554 (1987); Kishimotoet al., Adv. Immunol. 46:149-182 (1989); Kishimotoet al., Cell 48:681-690 (1987); Ruoslahtiet al., Science 238:491-497 (1987).
Integrins are a class of membrane-spanning heterodimers comprising an α subunit in noncovalent association with a β subunit. The β subunits are generally capable of association with more than one α subunit and the heterodimers sharing a common β subunit have been classified as subfamilies within the integrin population (Larson and Springer, “Structure and function of leukocyte integrins,” Immunol. Rev. 114:181-217 (1990)).
The integrin molecules of the CD11/CD18 family, and their cellular ligands, have been found to mediate a variety of cell-cell interactions, especially in inflammation. These proteins have been demonstrated to be critical for adhesive functions in the immune system (Kishimotoet al., Adv. Immunol. 46:149-182 (1989)). Monoclonal antibodies to LFA-1 have been shown to block leukocyte adhesion to endothelial cells (Dustin et al., J. Cell. Biol. 107:321-331 (1988); Smith et al., J. Clin. Invest. 83:2008-2017 (1989)) and to inhibit T-cell activation (Kuypers et al., Res. Immunol., 140:461 (1989)), conjugate formation required for antigen-specific CTL killing (Kishimotoet al., Adv. Immunol. 46:149-182 (1989)), T. cell proliferation (Davignonet al., J. Immunol. 127:590-595 (1981)) and NK cell killing (Krenskyet al., J. Immunol. 131:611-616 (1983)).
ICAMs
ICAM-1 (CD54) is a cell surface adhesion receptor that is a member of the immunoglobulin protein super-family (Rothleinet al., J. Immunol. 137:1270-1274 (1986); Stauntonet al., Cell 52:925-933 (1988). Members of this superfamily are characterized by the presence of one or more Ig homology regions, each consisting of a disulfide-bridged loop that has a number of anti-parallel β-pleated strands arranged in two sheets. Three types of homology regions have been identified, each with a typical length and having a consensus sequence of amino acid residues located between the cysteines of the disulfide bond (Williams, A. F. et al. Ann Rev. Immunol. 6:381-405 (1988); Hunkapillar, T. et al. Adv. Immunol. 44:1-63 (1989). ICAM-1 is expressed on a variety of hematopoietic and non-hematopoietic cells and is upregulated at sites of inflammation by a variety of inflammatory mediators (Dustin et al., J. Immunol., 137:256-254 (1986)). ICAM-1 is a 90,000-110,000 Mr glycoprotein with a low messenger RNA levels and moderate surface expression on unstimulated endothelial cells. LPS, IL-1 and TNF strongly upregulate ICAM-1 mRNA and surface expression with peak expression at approximately 18-24 hours (Dustinet al., J. Cell. Biol. 107:321-331 (1988); Stauntonet al., Cell 52:925-933 (1988)). ICAM-1 has five extracellular Ig like domains (designated Domains 1, 2, 3, 4 and 5 or D1, D2, D3, D4 and D5) and an intracellular or cytoplasmic domain. The structures and sequence of the domains is described by Staunton et al. (Cell 52:925-933 (1988)).
ICAM-1 was defined originally as a counter-receptor for LFA-1 (Springer et al., Ann. Rev. Immunol, 5:223-252 (1987); Marlin Cell 51:813-819 (1987); Simmonset al., Nature 331:624-627 (1988); Staunton Nature 339:61-64 (1989); Stauntonet al., Cell 52:925-933 (1988)). The LFA-1/ICAM-1 interaction is known to be at least partially responsible for lymphocyte adhesion (Dustinet al., J. Cell. Biol. 107:321-331 (1988); Mentzeret al., J. Cell. Physiol. 126:285-290 (1986)), monocyte adhesion (Amaoutet al., J. Cell Physiol. 137:305 (1988); Mentzeret al., J. Cell. Physiol. 130:410-415 (1987); te Veldeet al., Immunology 61:261-267 (1987)), and neutrophil adhesion (Loet al., J. Immunol. 143(10):3325-3329 (1989); Smith et al., J. Clin. Invest. 83:2008-2017 (1989)) to endothelial cells. Through the development of function blocking monoclonal antibodies to ICAM-1 additional ligands for LFA-1 were identified, ICAM-2 and ICAM-3 (Simmons, Cancer Surveys 24, Cell Adhesion and Cancer, 1995) that mediate the adhesion of lymphocytes to other leukocytes as well as non-hematopoietic cells. Interactions of LFA-1 with ICAM-2 are thought to mediate natural killer cell activity (Helander et al., Nature 382:265-267 (1996)) and ICAM-3 binding is thought to play a role in lymphocyte activation and the initiation of the immune response (Simmons, ibid). The precise role of these ligands in normal and aberrant immune responses remains to be defined.
Disorders Mediated by T Lymphocytes
Function blocking monoclonal antibodies have shown that LFA-1 is important in T-lymphocyte-mediated killing, T-helper lymphocyte responses, natural killing, and antibody-dependent killing (Springer et al., Ann. Rev. Immunol 5:223-252 (1987)). Adhesion to the target cell as well as activation and signaling are steps that are blocked by antibodies against LFA-1.
Many disorders and diseases are mediated through T lymphocytes and treatment of these diseases have been addressed through many routes. Rheumatoid arthritis (RA) is one such disorder. Current therapy for RA includes bed rest, application of heat, and drugs. Salicylate is the currently preferred treatment drug, particularly as other alternatives such as immunosuppressive agents and adrenocorticosteroids can cause greater morbidity than the underlying disease itself. Nonsteroidal anti-inflammatory drugs are available, and many of them have effective analgesic, anti-pyretic and anti-inflammatory activity in RA patients. These include cyclosporin, indomethacin, phenylbutazone, phenylacetic acid derivatives such as ibuprofen and fenoprofen, naphthalene acetic acids (naproxen), pyrrolealkanoic acid (tometin), indoleacetic acids (sulindac), halogenated anthranilic acid (meclofenamate sodium), piroxicam, and diflunisal. Other drugs for use in RA include anti-malarials such as chloroquine, gold salts and penicillamine. These alternatives frequently produce severe side effects, including retinal lesions and kidney and bone marrow toxicity. Immunosuppressive agents such as methotrexate have been used only in the treatment of severe and unremitting RA because of their toxicity. Corticosteroids also are responsible for undesirable side effects (e.g., cataracts, osteoporosis, and Cushing's disease syndrome) and are not well tolerated in many RA patients.
Another disorder mediated by T lymphocytes is host rejection of grafts after transplantation. Attempts to prolong the survival of transplanted allografts and xenografts, or to prevent host versus graft rejection, both in experimental models and in medical practice, have centered mainly on the suppression of the immune apparatus of the host/recipient. This treatment has as its aim preventive immunosuppression and/or treatment of graft rejection. Examples of agents used for preventive immunosuppression include cytotoxic drugs, anti-metabolites, corticosteroids, and anti-lymphocytic serum. Nonspecific immunosuppressive agents found particularly effective in preventive immunosuppression (azathioprine, bromocryptine, methylprednisolone, prednisone, and most recently, cyclosporin A) have significantly improved the clinical success of transplantation. The nephrotoxicity of cyclosporin A after renal transplantation has been reduced by co-administration of steroids such as prednisolone, or prednisolone in conjunction with azathioprine. In addition, kidneys have been grafted successfully using anti-lymphocyte globulin followed by cyclosporin A. Another protocol being evaluated is total lymphoid irradiation of the recipient prior to transplantation followed by minimal immunosuppression after transplantation.
Treatment of rejection has involved use of steroids, 2-amino-6-aryl-5-substituted pyrimidines, heterologous anti-lymphocyte globulin, and monoclonal antibodies to various leukocyte populations, including OKT-3. See generally J. Pediatrics, 111: 1004-1007 (1987), and specifically U.S. Pat. No. 4,665,077.
The principal complication of immunosuppressive drugs is infections. Additionally, systemic immunosuppression is accompanied by undesirable toxic effects (e.g., nephrotoxicity when cyclosporin A is used after renal transplantation) and reduction in the level of the hemopoietic stem cells. Immunosuppressive drugs may also lead to obesity, poor wound healing, steroid hyperglycemia, steroid psychosis, leukopenia, gastrointestinal bleeding, lymphoma, and hypertension.
In view of these complications, transplantation immunologists have sought methods for suppressing immune responsiveness in an antigen-specific manner (so that only the response to the donor alloantigen would be lost). In addition, physicians specializing in autoimmune disease strive for methods to suppress autoimmune responsiveness so that only the response to the self-antigen is lost. Such specific immunosuppression generally has been achieved by modifying either the antigenicity of the tissue to be grafted or the specific cells capable of mediating rejection. In certain instances, whether immunity or tolerance will be induced depends on the manner in which the antigen is presented to the immune system.
Pretreating the allograft tissues by growth in tissue culture before transplantation has been found in two murine model systems to lead to permanent acceptance across MHC barriers. Lafferty et al., Transplantation, 22:138-149 (1976); Bowen et al., Lancet, 2:585-586 (1979). It has been hypothesized that such treatment results in the depletion of passenger lymphoid cells and thus the absence of a stimulator cell population necessary for tissue immunogenicity. Lafferty et al., Annu. Rev. Immunol., 1:143 (1983). See also Lafferty et al., Science, 188:259-261 (1975) (thyroid held in organ culture), and Gores et al., J. Immunol., 137:1482-1485 (1986) and Faustman et al., Proc. Natl. Acad. Sci. U.S.A., 78: 5156-5159 (1981) (islet cells treated with murine anti-Ia antisera and complement before transplantation). Also, thyroids taken from donor animals pretreated with lymphocytotoxic drugs and gamma radiation and cultured for ten days in vitro were not rejected by any normal allogeneic recipient (Gose and Bach, J. Exp. Med., 149:1254-1259 (1979)). All of these techniques involve depletion or removal of donor lymphocyte cells.
In some models such as vascular and kidney grafts, there exists a correlation between Class II matching and prolonged allograft survival, a correlation not present in skin grafts (Pescovitz et al., J. Exp. Med., 160:1495-1508 (1984); Conti et al., Transplant. Proc., 19: 652-654 (1987)). Therefore, donor-recipient HLA matching has been utilized. Additionally, blood transfusions prior to transplantation have been found to be effective (Opelz et al., Transplant. Proc., 4: 253 (1973); Persijn et al., Transplant. Proc., 23:396 (1979)). The combination of blood transfusion before transplantation, donor-recipient HLA matching, and immunosuppression therapy (cyclosporin A) after transplantation was found to improve significantly the rate of graft survival, and the effects were found to be additive (Opelz et al., Transplant. Proc., 17:2179 (1985)).
The transplantation response may also be modified by antibodies directed at immune receptors for MHC antigens (Bluestone et al., Immunol. Rev. 90:5-27 (1986)). Further, graft survival can be prolonged in the presence of antigraft antibodies, which lead to a host reaction that in turn produces specific immunosuppression (Lancaster et al., Nature, 315: 336-337 (1985)). The immune response of the host to MHC antigens may be modified specifically by using bone marrow transplantation as a preparative procedure for organ grafting. Thus, anti-T-cell monoclonal antibodies are used to deplete mature T-cells from the donor marrow inoculum to allow bone marrow transplantation without incurring graft-versus-host disease (Mueller-Ruchholtz et al., Transplant Proc., 8:537-541 (1976)). In addition, elements of the host's lymphoid cells that remain for bone marrow transplantation solve the problem of immunoincompetence occurring when fully allogeneic transplants are used.
As shown in FIG. 1, lymphocyte adherence to endothelium is a key event in the process of inflammation. There are at least three known pathways of lymphocyte adherence to endothelium, depending on the activation state of the T-cell and the endothelial cell. T-cell immune recognition requires the contribution of the T-cell receptor as well as adhesion receptors, which promote attachment of—cells to antigen-presenting cells and transduce regulatory signals for T-cell activation. The lymphocyte function associated (LFA) antigen-1 (LFA-1, CD11a/CD18, αLβ2: where αL is CD11a and β2 is CD18) has been identified as the major integrin receptor on lymphocytes involved in these cell adherence interactions leading to several pathological states. ICAM-1, the endothelial cell immunoglobulin-like adhesion molecule, is a known ligand for LFA-1 and is implicated directly in graft rejection, psoriasis, and arthritis.
LFA-1 is required for a range of leukocyte functions, including lymphokine production of helper T-cells in response to antigen-presenting cells, killer T-cell-mediated target cell lysis, and immunoglobulin production through T-cell/B-cell interactions. Activation of antigen receptors on T-cells and B-cells allows LFA-1 to bind its ligand with higher affinity.
Monoclonal antibodies (MAbs) directed against LFA-1 led to the initial identification and investigation of the function of LFA-1 (Davignon et al., J. Immunol., 127:590 (1981)). LFA-1 is present only on leukocytes (Krenskey et al., J. Immunol., 131:611 (1983)), and ICAM-1 is distributed on activated leukocytes, dermal fibroblasts, and endothelium (Dustin et al., J. Immunol. 137:245 (1986)).
Previous studies have investigated the effects of anti-CD11a MAbs on many T-cell-dependent immune functions in vitro and a limited number of immune responses in vivo. In vitro, anti-CD11a MAbs inhibit T-cell activation (Kuypers et al., Res. Immunol., 140:461 (1989)), T-cell-dependent B-cell proliferation and differentiation (Davignon et al., supra; Fischer et al., J. Immunol., 136:3198 (1986)), target cell lysis by cytotoxic T-lymphocytes (Krensky et al., supra), formation of immune conjugates (Sanders et al., J. Immunol., 137:2395 (1986); Mentzer et al., J. Immunol., 135:9 (1985)), and the adhesion of T-cells to vascular endothelium (Lo et al., J. Immunol., 143:3325 (1989)). Also, the antibody 5C6 directed against CD11b/CD18 was found to prevent intra-islet infiltration by both macrophages and T cells and to inhibit development of insulin-dependent diabetes mellitis in mice (Hutchings et al., Nature, 348: 639 (1990)).
The observation that LFA-1:ICAM-1 interaction is necessary to optimize T-cell function in vitro, and that anti-CD11a MAbs induce tolerance to protein antigens (Benjamin et al., Eur. J. Immunol., 18:1079 (1988)) and prolongs tumor graft survival in mice (Heagy et al., Transplantation, 37: 520-523 (1984)) was the basis for testing the MAbs to these molecules for prevention of graft rejection in humans.
Experiments have also been carried out in primates. For example, based on experiments in monkeys it has been suggested that a MAb directed against ICAM-1 can prevent or even reverse kidney graft rejection (Cosimi et al., “Immunosuppression of Cynomolgus Recipients of Renal Allografts by R6.5, a Monoclonal Antibody to Intercellular Adhesion Molecule-1,” in Springer et al. (eds.), Leukocyte Adhesion Molecules New York: Springer, (1988), p. 274; Cosimi et al., J. Immunology, 144:4604-4612 (1990)). Furthermore, the in vivo administration of anti-CD11a MAb to cynomolgus monkeys prolonged skin allograft survival (Berlin et al., Transplantation, 53: 840-849 (1992)).
The first successful use of a rat anti-murine CD11a antibody (25-3; IgG1) in children with inherited disease to prevent the rejection of bone-marrow-mismatched haploidentical grafts was reported by Fischer et al., Lancet, 2: 1058 (1986). Minimal side effects were observed. See also Fischer et al., Blood, 77: 249 (1991); van Dijken et al., Transplantation, 49:882 (1990); and Perez et al., Bone Marrow Transplantation, 4:379 (1989). Furthermore, the antibody 25-3 was effective in controlling steroid-resistant acute graft-versus-host disease in humans (Stoppa et al., Transplant. Int., 4:3-7 (1991)).
However, these results were not reproducible in leukemic adult grafting with this MAb (Maraninchi et al., Bone Marrow Transplant, 4:147-150 (1989)), or with an anti-CD18 MAb, directed against the invariant chain of LFA-1, in another pilot study (Baume et al., Transplantation, 47: 472 (1989)). Furthermore, a rat anti-murine CD11a MAb, 25-3, was unable to control the course of acute rejection in human kidney transplantation (LeMauff et al., Transplantation, 52: 291 (1991)).
A review of the use of monoclonal antibodies in human transplantation is provided by Dantal and Soulillou, Current Opinion in Immunology, 3:740-747 (1991). An earlier report showed that brief treatment with either anti-LFA-1 or anti-ICAM-1 MAbs minimally prolonged the survival of primarily vascularized heterotopic heart allografts in mice (Isobe et al., Science, 255:1125 (1992)). However, combined treatment with both MAbs was required to achieve long-term graft survival in this model.
Independently, it was shown that treatment with anti-LFA-1 MAb alone potently and effectively prolongs the survival of heterotopic (ear-pinnae) nonprimarily vascularized mouse heart grafts using a maximum dose of 4 mg/kg/day and treatment once a week after a daily dose (Nakakura et al., J. Heart Lung Transplant., 11:223 (1992)). Nonprimarily vascularized heart allografts are more immunogenic and more resistant to prolongation of survival by MAbs than primarily vascularized heart allografts (Warren et al., Transplant. Proc., 5:717 (1973); Trager et al., Transplantation, 47:587 (1989)). The latter reference discusses treatment with L3T4 antibodies using a high initial dose and a lower subsequent dose.
Another study on treating a sclerosis-type disease in rodents using similar antibodies to those used by Nakakura et al., supra, is reported by Yednock et al., Nature, 356:63-66 (1992). Additional disclosures on the use of anti-LFA-1 antibodies and ICAM-1, ICAM-2, and ICAM-3 and their antibodies to treat LFA-1-mediated disorders include WO 91/18011 published Nov. 28, 1991, WO 91/16928 published Nov. 14, 1991, WO 91/16927 published Nov. 14, 1991, Can. Pat. Appln. 2,008,368 published Jun. 13, 1991, WO 90/03400, WO 90/15076 published Dec. 13, 1990, WO 90/10652 published Sep. 20, 1990, EP 387,668 published Sep. 19, 1990, WO 90/08187 published Jul. 26, 1990, WO 90/13281, WO 90/13316, WO 90/13281, WO 93/06864, WO 93/21953, WO 93/13210, WO 94/11400, EP 379,904 published Aug. 1, 1990, EP 346,078 published Dec. 13, 1989, U.S. Pat. No. 5,002,869, U.S. Pat. No. 5,071,964, U.S. Pat. No. 5,209,928, U.S. Pat. No. 5,223,396, U.S. Pat. No. 5,235,049, U.S. Pat. No. 5,284,931, U.S. Pat. No. 5,288,854, U.S. Pat. No. 5,354,659, Australian Pat. Appln. 15518/88 published Nov. 10, 1988, EP 289,949 published Nov. 9, 1988, and EP 303,692 published Feb. 22, 1989, EP 365,837, EP 314,863, EP 319,815, EP 468, 257, EP 362,526, EP 362, 531, EP 438,310.
Other disclosures on the use of LFA-1 and ICAM peptide fragments and antagonists include; U.S. Pat. No. 5,149,780, U.S. Pat. No. 5,288,854, U.S. Pat. No. 5,340,800, U.S. Pat. No. 5,424,399, U.S. Pat. No. 5,470,953, WO 90/03400, WO 90/13316, WO 90/10652, WO 91/19511, WO 92/03473, WO 94/11400, WO 95/28170, JP 4193895, EP 314,863, EP 362,526 and EP 362,531.
The above methods successfully utilizing anti-LFA-1 or anti-ICAM-1 antibodies, LFA-1 or ICAM-1 peptides, fragments or peptide antagonists represent an improvement over traditional immunosuppressive drug therapy. These studies demonstrate that LFA-1 and ICAM-1 are appropriate targets for antagonism. There is a need in the art to better treat disorders that are mediated by LFA-1 including autoimmune diseases, graft vs. host or host vs. graft rejection, and T-cell inflammatory responses, so as to minimize side effects and sustain specific tolerance to self- or xenoantigens. There is also a need in the art to provide a non-peptide antagonists to the LFA-1:ICAM-1 interaction.
Albumin is an abundant plasma protein which is responsible for the transport of fatty acids. However, albumin also binds and perturbs the pharmacokinetics of a wide range of drug compounds. Accordingly, a significant factor in the pharmacological profile of any drug is its binding characteristics with respect to serum plasma proteins such as albumin. A drug compound may have such great affinity for plasma proteins that it is not be available in serum to interact with its target tissue, cell or protein. For example, a compound for which 99% binds to plasma protein upon administration will have half the concentration available in plasma to interact with its target than a compound which binds only 98%. Accordingly it would be desirable to provide LFA antagonist compounds which have low serum plasma protein binding affinity.